28,415 research outputs found
Recommended from our members
Directed Placement for mVLSI Devices
Continuous-flow microfluidic devices based on integrated channel networks are becoming increasingly prevalent in research in the biological sciences. At present, these devices are physically laid out by hand by domain experts who understand both the underlying technology and the biological functions that will execute on fabricated devices. The lack of a design science that is specific to microfluidic technology creates a substantial barrier to entry. To address this concern, this article introduces Directed Placement, a physical design algorithm that leverages the natural "directedness" in most modern microfluidic designs: fluid enters at designated inputs, flows through a linear or tree-based network of channels and fluidic components, and exits the device at dedicated outputs. Directed placement creates physical layouts that share many principle similarities to those created by domain experts. Directed placement allows components to be placed closer to their neighbors compared to existing layout algorithms based on planar graph embedding or simulated annealing, leading to an average reduction in laid-out fluid channel length of 91% while improving area utilization by 8% on average. Directed placement is compatible with both passive and active microfluidic devices and is compatible with a variety of mainstream manufacturing technologies
NuSTAR and Swift observations of Swift J1357.2-0933 during an early phase of its 2017 outburst
We present a detailed spectral analysis of Swift and NuSTAR observations of
the very faint X-ray transient and black hole system Swift J1357.2-0933 during
an early low hard state of its 2017 outburst. Swift J1357.2-0933 was observed
at 0.02% of the Eddington luminosity (for a distance of 2.3 kpc and a
mass of 4 M). Despite the low luminosity, the broadband X-ray
spectrum between 0.3 and 78 keV requires the presence of a disk blackbody
component with an inner disk temperature of T 0.06 keV
in addition to a thermal Comptonization component with a photon index of
{\Gamma} 1.70. Using a more physical model, which takes strong
relativistic effects into account, and assuming a high inclination of
70, which is motivated by the presence of dips in optical light curves,
we find that the accretion disk is truncated within a few RISCO from the black
hole, independent of the spin.Comment: 11 pages, 5 figures, accepted for publication in Ap
Peculiar outbursts of an ultra luminous source likely signs of an aperiodic disc-wind
The metal rich globular cluster RZ 2109 in the massive Virgo elliptical
galaxy NGC 4472 (M49) harbours the ultra luminous X-ray source XMMU
122939.7+075333. Previous studies showed that this source varies between bright
and faint phases on timescales of just a few hours. Here, we report the
discovery of two peculiar X-ray bursting events that last for about 8 and 3.5
hours separated by about 3 days. Such a recurring X-ray burst-like behaviour
has never been observed before. We argue that type-I X-ray bursts or super
bursts as well as outburst scenarios requiring a young stellar object are
highly unlikely explanations for the observed light curve, leaving an aperiodic
disc wind scenario driven by hyper-Eddington accretion as a viable explanation
for this new type of X-ray flaring activities.Comment: 7 pages, 2 figures, accepted by Ap
The Discovery of Quasisoft and Supersoft Sources in External Galaxies
We apply a uniform procedure to select very soft sources from point sources
observed by Chandra in 4 galaxies. This sample includes one elliptical galaxy
(NGC 4967), 2 face-on spirals (M101 and M83), and an interacting galaxy (M51).
We have found very soft X-ray sources (VSSs) in every galaxy. Some of these fit
the criteria for canonical supersoft sources (SSSs), while others are somewhat
harder. These latter have characteristic values of kT < 300 eV; we refer to
them as quasisoft sources (QSSs). We found a combined total of 149 VSSs in the
4 galaxies we considered; 77 were SSSs and 72 were QSSs. (See the paper for the
original long abstract)Comment: 20 pages, 6 figures. Accepted for publication in Ap
- …